To uncover many car problems at his four Massachusetts and Rhode Island repair shops, Stan Morin exchanges small gifts with friends at local dealerships. It's not that Mr. Morin or his mechanics lack the qualifications to diagnose car troubles, rather they say they can't get the same service information provided to dealerships.

Morin spends thousands of dollars a year to subscribe to manufacturer websites, but his diagnostic reports sometimes have nearly 20 pages less than those provided to dealers – pages that can mean the difference between finding the problem or referring the customer to another shop. So, he's forced to barter with dealership mechanics for access to their computerized diagnostic tools to keep his customers. "I need to do what I need to do to survive as a businessman," says Morin.

Many independent mechanics charge that, as cars have become more advanced, manufacturers have limited their access to engine computers, impeding repairs and forcing drivers to seek the help of an authorized dealership. That could lead to higher prices for repairs, mechanics say, a prospect to which they say drivers already pumping more of their paychecks into their cars should pay attention. Manufacturers insist that mechanics are given all the information required to make repairs and only stopped from accessing sensitive information, such as part blueprints or security information.

"As cars get more sophisticated, the car companies have a huge amount of control over who has access to the systems," says Aaron Lowe of the Automotive Aftermarket Industry Association, based in Bethesda, Md., which represents independent auto shops and parts manufacturers. "Whether intentionally or unintentionally, they could make it difficult for the independent aftermarket to repair cars now and into the future."

That's why some lawmakers are pushing for right to repair laws. Rep. Edolphus Towns (D) of New York introduced a bill that would force manufacturers to provide the same information and diagnostic tools to independent repair shops and dealers alike, but the bill is unlikely to reach the House floor anytime soon. Last year, the Nevada legislature passed a resolution that called on car companies to make diagnostic tools and information available to independent garages. Similar legislation is active in Massachusetts and New Jersey.

At his auto shop in Randolph, Mass., Bill Cahill says that daily he and his mechanics encounter problems that require diagnostic tools or information unavailable to them. Often, he's been forced to send customers to the dealer, which he says unfairly discredits him.

"They're creating an unlevel playing field and developing a competitive edge for their dealerships," says Mr. Cahill.

Manufacturers and dealers say that the charges are unfounded. Already, independent repair shops complete more than 75 percent of all nonwarranty repairs.

"There are more vehicle repairs out there than what any given body can handle," says Mike Stanton, president of the Association of International Automobile Manufacturers in Arlington, Va. "The most important thing for our member companies is that people have a good, satisfactory relationship with their vehicles so that they'll buy another one hopefully from the same manufacturer. So it's in every manufacturers' interest to make sure that vehicles can be repaired quickly and easily."

Independent parts manufacturers may be the real force behind the right to repair movement, says Bailey Wood, spokesman for the National Automobile Dealers Association in McLean, Va. The main information withheld from the aftermarket protects part-design information, says Mr. Wood. "They invest millions of dollars overseas remanufacturing parts ... but if they were handed the blueprints, just think of the millions they'd save."

Additionally, the National Automotive Service Task Force has been created for independent mechanics to report any missing service information, but it remains largely unutilized. In 2006, the nonprofit organization received only 32 complaints. Cahill says many mechanics like himself think the organization is ineffective and don't want to give it legitimacy by using it, while others had never heard of it. Wood says the problem will not be solved unless the aftermarket begins working with groups like NASTF.